(p. 80) In his extraordinary book Mapping Human History, the science writer Steve Olson estimates that 80 billion “modern” humans–from the first beings recognizable as our forebears to the advent of Homo sapiens sapiens, our official name–have walked the earth down through the millennia. Supposing this number is correct, the men and women at middle-class standards or above in the United States and the European Union now live better than 99.4 percent of the human beings who have ever existed.
Source:
Easterbrook, Gregg. The Progress Paradox: How Life Gets Better While People Feel Worse. Paperback ed. New York: Random House, 2004.
The Olson book mentioned is:
Olson, Steve. Mapping Human History: Discovering the Past through Our Genes. New York: Houghton Mifflin Company, 2002.
(Note: italics in original.)